Recently, a heterogeneous network (sometimes abbreviated “HetNet”) is proposed in which multiple types of radio base stations (macro base stations, pico base stations, femto base stations, remote radio heads, etc.) having different radio capabilities, are deployed in a multi-layered way. In a heterogeneous network, base stations having a higher radio capability (the maximum transmission power, average transmission power, etc.), e.g., macro base stations are likely to be selected as the radio access points in accordance with reception power at the stage of cell search or handover in comparison with other base stations having a lower radio capability, e.g., pico base stations. Accordingly, connections of mobile stations are concentrated on base stations with higher radio capability, and thus, there is a tendency for excessive communication load at base stations with higher radio capability.
In order to solve the problem, for example, Patent Document 1 discloses a technology for controlling to change communication cell boundaries by changing an offset value (bias value) that is used for numerically reducing the power level received at mobile stations, according to parameters, such as the load of the radio communication system and the amount of traffic. The mobile station in Patent Document 1 selects its serving base station (a macro cell base station or a micro cell base station) on the basis of the offset power level (reception power).